There are two 2017 Crosstrail Elites: aluminum and carbon-framed. I suspect the OP is thinking of the former.

Trek DS4 or Crosstrail Elite (aluminum)? Components are a wash. Frames are likely equivalent in quality/weight; aesthetics are a matter of personal preference. Personally, I think the current Trek DS frame, with that kinked downtube, is hideous -- but that means nothing to anyone except me.

Two things differentiate these bikes substantively: geometry and fork. The geometries are different; again, the only way to choose between the two is personal test riding/figuring out fit. The forks are a different matter. I have ridden the Crosstrail Elite with the Specialized-modified Brain fork.

It works, and effectively negates the need for a lockout. The concept is simple in concept, though difficult in execution as travbikeman noted. The fork's hydraulic damper has an inertial valve built into it. The suspension is inactive (in effect, locked out) until the fork hits a bump. When it does, the inertial valve opens and the fork responds. There is no noticeable lag. Bump past, the valve closes.

To my mind this is an excellent application of this technology -- that is, to this kind of cross-terrain bike. My only criticism: the two carbon-framed models should have the air-spring version of this fork (Suntour NRX).